Hi,
I am new, and wondered if you can help? What is an ECU upgrade? I have seen an MKV for sale, but it states its ECU light is on, and needs an upgrade?
Is this an expensive job?
cheers peeps
Lippy 
The regular greeters have not said hello yet so welcome to the forum...
I'm not sure if by upgrade they mean replacement... either way its not cheap so only the car being super cheap could justify buying it. The other issue is that how can you be sure that's the only issue without getting a professional to inspect it. Is the problem that the light is just on or does it have running issues too?
You could pop this question into the MK5 section, they maybe able to give you some more info..
